前端JavaScript入门到精通，javascript核心进阶ES6语法、API、js高级等基础知识和实战 —— JS进阶（二）

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  <title>Document</title>
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<body>
  <script>
    const arr = [{
      name: '张三',
      salary: 10000
    }, {
      name: '李四',
      salary: 10000
    }, {
      name: '王五',
      salary: 20000
    },
    ]
    // 涨薪的钱数  10000 * 0.3 
    // const money = arr.reduce(function (prev, item) {
    //   return prev + item.salary * 0.3
    // }, 0)
    const money = arr.reduce((prev, item) => prev + item.salary * 0.3, 0)
    console.log(money)
  </script>
</body>
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  <meta http-equiv="X-UA-Compatible" content="IE=edge">
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  <title>Document</title>
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<body>
  <script>
    // const arr = ['red', 'blue', 'green']
    // const re = arr.find(function (item) {
    //   return item === 'blue'
    // })
    // console.log(re)
    const arr = [
      {
        name: '小米',
        price: 1999
      },
      {
        name: '华为',
        price: 3999
      },
    ]
    // 找小米 这个对象，并且返回这个对象
    // const mi = arr.find(function (item) {
    //   // console.log(item)  //
    //   // console.log(item.name)  //
    //   console.log(111)
    //   return item.name === '华为'
    // })
    // 1. find 查找
    // const mi = arr.find(item => item.name === '小米')
    // console.log(mi)
    // 2. every 每一个是否都符合条件，如果都符合返回 true ，否则返回false
    const arr1 = [10, 20, 30]
    const flag = arr1.every(item => item >= 20)
    console.log(flag)
  </script>
</body>
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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div></div>
  <script>
    const spec = { size: '40cm*40cm', color: '黑色' }
    //1. 所有的属性值回去过来  数组
    // console.log(Object.values(spec))
    // 2. 转换为字符串   数组join('/') 把数组根据分隔符转换为字符串
    // console.log(Object.values(spec).join('/'))
    document.querySelector('div').innerHTML = Object.values(spec).join('/')
  </script>
</body>
</html>

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<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
  </ul>
  <script>
    //  Array.from(lis) 把伪数组转换为真数组
    const lis = document.querySelectorAll('ul li')
    // console.log(lis)
    // lis.pop() 报错
    const liss = Array.from(lis)
    liss.pop()
    console.log(liss)
  </script>
</body>
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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    //1. split 把字符串 转换为 数组  和 join() 相反
    // const str = 'pink,red'
    // const arr = str.split(',')
    // console.log(arr)
    // const str1 = '2022-4-8'
    // const arr1 = str1.split('-')
    // console.log(arr1)
    // 2. 字符串的截取   substring(开始的索引号[， 结束的索引号])
    // 2.1 如果省略 结束的索引号，默认取到最后
    // 2.2 结束的索引号不包含想要截取的部分
    // const str = '今天又要做核酸了'
    // console.log(str.substring(5, 7))
    // 3. startsWith 判断是不是以某个字符开头
    // const str = 'pink老师上课中'
    // console.log(str.startsWith('pink'))
    // 4. includes 判断某个字符是不是包含在一个字符串里面
    const str = '我是pink老师'
    console.log(str.includes('pink')) // true
  </script>
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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div></div>
  <script>
    const gift = '50g的茶叶,清洗球'
    // 1. 把字符串拆分为数组
    // console.log(gift.split(',')) [,]
    // 2. 根据数组元素的个数，生成 对应 span标签
    // const str = gift.split(',').map(function (item) {
    //   return `<span>【赠品】 ${item}</span> <br>`
    // }).join('')
    // // console.log(str)
    // document.querySelector('div').innerHTML = str
    document.querySelector('div').innerHTML = gift.split(',').map(item => `<span>【赠品】 ${item}</span> <br>`).join('')
  </script>
</body>
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<script>
    const goodsList = [
      {
        id: '4001172',
        name: '称心如意手摇咖啡磨豆机咖啡豆研磨机',
        price: 289.9,
        picture: 'https://yanxuan-item.nosdn.127.net/84a59ff9c58a77032564e61f716846d6.jpg',
        count: 2,
        spec: { color: '白色' }
      },
      {
        id: '4001009',
        name: '竹制干泡茶盘正方形沥水茶台品茶盘',
        price: 109.8,
        picture: 'https://yanxuan-item.nosdn.127.net/2d942d6bc94f1e230763e1a5a3b379e1.png',
        count: 3,
        spec: { size: '40cm*40cm', color: '黑色' }
      },
      {
        id: '4001874',
        name: '古法温酒汝瓷酒具套装白酒杯莲花温酒器',
        price: 488,
        picture: 'https://yanxuan-item.nosdn.127.net/44e51622800e4fceb6bee8e616da85fd.png',
        count: 1,
        spec: { color: '青色', sum: '一大四小' }
      },
      {
        id: '4001649',
        name: '大师监制龙泉青瓷茶叶罐',
        price: 139,
        picture: 'https://yanxuan-item.nosdn.127.net/4356c9fc150753775fe56b465314f1eb.png',
        count: 1,
        spec: { size: '小号', color: '紫色' },
        gift: '50g茶叶,清洗球,宝马, 奔驰'
      }
    ]
    // 1. 根据数据渲染页面
    document.querySelector('.list').innerHTML = goodsList.map(item => {
      // console.log(item)  // 每一条对象
      // 对象解构  item.price item.count
      const { picture, name, count, price, spec, gift } = item
      // 规格文字模块处理
      const text = Object.values(spec).join('/')
      // 计算小计模块 单价 * 数量  保留两位小数 
      // 注意精度问题，因为保留两位小数，所以乘以 100  最后除以100
      const subTotal = ((price * 100 * count) / 100).toFixed(2)
      // 处理赠品模块 '50g茶叶,清洗球'
      const str = gift ? gift.split(',').map(item => `<span class="tag">【赠品】${item}</span> `).join('') : ''
      return `
        <div class="item">
          <img src=${picture} alt="">
          <p class="name">${name} ${str} </p>
          <p class="spec">${text} </p>
          <p class="price">${price.toFixed(2)}</p>
          <p class="count">x${count}</p>
          <p class="sub-total">${subTotal}</p>
        </div>
      `
    }).join('')
    // 3. 合计模块
    const total = goodsList.reduce((prev, item) => prev + (item.price * 100 * item.count) / 100, 0)
    // console.log(total)
    document.querySelector('.amount').innerHTML = total.toFixed(2)
  </script>

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<head>
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  <title>Document</title>
</head>
<body>
  <script>
    const num = 10
    console.log(String(num)) 
    console.log(num.toString())
  </script>
</body>
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